The present invention relates to an inorganic glass which is provided with water repellence that is produced by ion irradiation upon or ion-implantation in the surface thereof.
When water sticks onto the surface of a glass window or a glass mirror of, for example, automotive vehicles, boats or buildings, visibility through the glass is obstructed.
Other than the mechanical wiping of the glass, the following three methods have been proposed to overcome the abovementioned problem:
(1) Water repellent treatment of the glass surface
(2) Hydrophile treatment of the glass surface
(3) Heating of the glass
In principle, each of these treatments improves the surface energy of the glass.
As examples of the first method, the glass surface is covered with an organo-silicone (Japanese Patent Kokoku Publication No. 50-15473), or is ion-implanted by semiconductor elements such as B or Si, N or Group 8 elements (in the International Periodic Table) in accordance with an ion-implantation technique utilized for semiconductor impurity doping (Japanese Patent Kokai Publication Nos. 56-84344, 57-11850, 57-11851). Other examples include the coating of a water repelling agent of an organo-silicone type or a fluorine type on the surface of the glass by either application or spray coating as well as coating the glass with a polymer film of a fluorocarbon type or a fluorine type on the basis of a plasma treatment technique (Japanese Patent Kokoku Publication No. 60-13065).
Examples of the second method include the coating of the glass surface with a hydrophilic surface-active agent, polyhydric alcohol, or hydrophilic polymer (Japanese Patent Kokai Publication No. 53-58492). In this method, the field of vision can be secured by wetting the surface of the glass.
With respect to the third method, a heat generating element is bonded onto the surface of glass to evaporate water by heat.
However, the above-mentioned methods involve the following problems:
The third method has a large energy consumption and is also high in cost due to the complexity of the manufacturing steps associated therewith. Further, because this method is not effective for repellence of large-diameter drops of water, this method has only a limited use.
In the second method, the durability of the treated layer on the glass surface is poor, therefore this method cannot be effectively employed in automotive vehicles which require particularly severe weather proofing characteristics.
With respect to the first method, the method of coating glass with organic silicon also provides poor durability with regard to the water repellent effect. Further, the conventional ion implantation method using Ni, P or Si is not practical because the weatherproof characteristics and the durability are not satisfactory.
In summary, glass which has been treated for water repellent and hydrophile characteristics in accordance with the above-mentioned methods are only partially effective for mirrors within, for example, bathrooms. Furthermore, the durability of the water repellence of the glass surface is low when the treated glass is used under severe outdoor environmental conditions. In particular, the durability of water repellent effect of the prior-art method is not sufficient when used within vehicles, ships, aircraft, etc. where severe weatherproof characteristics and strong wear resistance are both required.